Process of and apparatus for strictly limited separation of mixtures by the speed of fall in liquid media



Sept. 16, 1952 2,610,737

T. EDER PROCESS OF AND APPARATUS FOR STRICTLY LIMITED SEPARATION OFMIXTURES BY THE SPEED OF FALL. IN LIQUID MEDIA Filed March 18, 1948 5Sheets-Sheet l By AGENTS T. EDER 2,610,737- PROCESS OF AND APPARATUS FORSTRICTLY LIMITED SEPARATION Sept. 16, 1952 OF MIXTURES BY THE SPEED OFFALL IN LIQUID MEDIA Filed March 18, 1948 I INVENTO-Er THEODOal EDER wmfi AGENTS 4 Sept. 16, 1952 T. EDER 2,610,737

PROCESS OF AND APPARATUS FOR STRICTLY LIMITED SEPARATION OF MIXTURES BYTHE SPEED OF FALL IN LIQUID MEDIA Filed March 18, 1948 5 Sheets-Sheet 3THEODOR ED R Br ,Jlo.

AGENTS Patented Sept. 16, 1952 UNITED" STATES FF'ICE" -2,610,7-3s I IPRooEss OFVAND. APPARATUS/FOR STRICT, LY LIMITED SEPARATION, OFMIXTURES; BX THE. sruen. 0F FALLIN- LIQ ID MEDIA Theodor Eder, Vienna,Application March 18, Serial fin'rliiifififl InJAustria November 1.1.1,1941 8-G1aims. (Cl. 20 9--.159')- According-tdtheirnown state of; theart, the classification by meansof screens is considered the most highlyselective method which has gained commercial success in sizing grains.

The technicardiiiiculties, however 'encountered iirtheclassification'by-the use of screens grow as the screening meshes;become finer; resulting in 1onger"scre ening time l'arger screeningsurfaces; or higher frequencies of vibration.

On the otheryhand; itis'known; to size finer materials in risingcurrents oiliquids; (-See, 6. g Ul-Sv Patents No. 636,615';' 948,513;1,210,916; nd, 1;9 2; 489 .r 1

The method'" of selectively classifying grain mixtures in rising-columnsof 'liquids, which has been madeavaiiab-le forcommerbia-l utilization,

is hereaiterfcalled vertical=separation;" thus dis tinguishing; from;separation methods using hori+ zontally moving liquids- (e; g;channel'sedimenta tioniof' kaolin sa-nd sizing; in spitzka'stens), whichmethodsarre de'uscri-bed'by reie'rence to their characteristic featureas fhorizontal' separation methods? g Though vertical separation methodsare more highly selective than methods-using horizontal separation,the-previouslyproposed methods for vertica-iseparation dd notbvenapproach the selectivity of screening. I

Another disadvantagesof the known methods of verticalt sepa'rationisthetlioss of reliability. of the. separating operation when the feed.concen- "rises small anrmimf tv only.- resultin nirnartsofithe coars st;enterin th fines or; imclQgging, up: the equipment. M

It: i the object, oi thisl-pinventon; -to;pro.videa process; forvertical separa ion; hi h pra t al y achievestthe same. selectiv y asthat. obtained by wet screening methods. amt-mor ov r r-su tr able forhighl oncentrated feeds, precludes clogging up; of'the apparatus: andrenders the selectivity obtained tq a high degree independent fromfluctuations in-thesupply' of the feed or of waterz h Verticalseparation is based"- aim-the principle'oi admitting the g-ranu-lanmaterial to be separated into a risihgncolumn of 1iqu-id,' e. g-.- atone half ofiihshei-ght, thee fines being carried: along by the risingcurrent to-=o.verflow;; (the coarsest falling against; the risin washwater and beingi removed from; the lower part. Qfwthfi; anus-rams Whenthe column; of liquid, asr proposed in many-cases; iscylindrical;throughout its height, suspended cushions ofgranu-lar material areIformed "e sp eciall'y---between" the-washing water and" feed inlets itthe-feed concentration rises by a smallamountonly; Suchfcushionsconsiderablyreducej-the selectivityoi! the; separation and fina-llycauseall coarses-to be carried upward, clear-water-only flowing out: throughthe coarse outlet; I

Actuadly, in a-vertical current flowing at'all altitudes with; the samezeed; granular material whose speed offall' equalsfthe vertical speed ofthe liquid is bound to fdrmvervhigh concentrations. r

The formationof suspendedcushions of falling grains is to beascribed-primarily to the, fact that the zones of increasedti'irbulemce,especially the water admission" zone in the lower part, are given ahigher carrying capacity, for; particles than would correspond tothe-average :vertical speed prevailingin i v 1 According tothisinvention the-formation of suspended cushionscfgrainsis-preVentedthereby that a suspension of'the'mixturefof grains tobe separated" isadmittedjto a current of a'liquid medium, suchjaswater;which is fed into the separator vessel ahajuniform rated and rises witha-'vertica1-velocity which increases continuously from the bottomtothetop ofth'e separator vesseli In those zones'of the separator vesselwhere the throug-hput-dfliquid is constant, the increasingvertical-velocity iseffected' by the cross section orfiow havingacontinuous, upward taper, whereas inthe zone; where the, suspension ofgrains is admitted to theseparator"vessel, the cross section of flowisincreased.

Onlvthe principle ofthe upwardly increasing verticalvelocitisjespeciallythe principle "of? the upward conicaltapen'overcomes "these" drawbacks. 7

' Ithas al'smbeen foundthat the usual methods or: admitting the materialto 'be'-*scp'arated lead to the; formation ofshii ting-bodiesof grains:These agglomerations ofsmalr grains fall against the rising liquidasthough they were large bodies. The .coarses i let :out. at" the bottomtherefore, contain; many lfin'essothat the: selectivity" isbackfisovercom'eainxthatthe suspension" of grains;

which is admitted to the rising current of liquid horizontally, isagitated and loosened up immediately before its admission by anadditional jet of water.

Another essential advantage can be achieved by rotating the risingcolumn of liquid about its vertical axis, either by admitting the liquidtangentially into the separator or, if the vertical velocities are verysmall, by agitating means. These measures on the one hand reduce theturbulence at the places of admission and on the other handsubstantially accelerate the even distribution of grains and water overthe whole cross-section of the liquid.

If, according to the invention, concentric annular guides are mountedabove the bottom water inlet in the direction of flow, these guides ifproperly arranged act as brakes for the central portion of the liquidwhich, not being affected by the friction of the separator walls, tendsto move more rapidly than the outer portions, and on the other hand tendto calm down the turbulence of the rising liquid to such an extent that,if the feed is not admitted at too high a. rate, the formation ofsuspended cushions only takes place when the water flows between thewater and feed inlets at velocities approaching the speed of fallcritical for the separation.

The reliability of operation of a vertical separation method depends notonly on the design of the separator vessel but requires that the waterand feed be supplied at a constant rate. Because of this dependence of avertical separator on an accurate and constant regulation of the ratesof admission, the rate of water admission is regulated according to theinvention in the device described hereafter by maintaining constant thedistance from the water level to the outlet into the air andcompensating any fluctuations in the supply of water by the overflow ofsurplus water, the air carried along in the metered water being removedin quieting chambers.

Some embodiments of the invention are illustrated by way of example inthe accompanying drawings, in which:

Fig. 1 is a vertical sectional view of an apparatus for verticalelutriation adapted for separation of sand of different sizes of grains,

Fig. 2 shows a modified detail,

Figs. 3 and 4 are cross-sections taken on the lines C-D and EF of Fig. 1respectively,

Figs. 5 and 6 are a vertical section and a top view respectively of anapparatus for vertical elutriation with a stirrer, adapted forseparation of kaolin and fine sand in great plants,

Figs. 7 and 8 are cross-sections taken on the lines G-H and JK of Fig. 5respectively,

Fig. 9 is a diagrammatic vertical sectional view of a modifiedconstruction of an apparatus for vertical elutriation for the aforesaidpurpose,

Fig. 10 is a cross-section taken on the line LK of Fig. 9, and

Fig. 11 is a diagrammatic view of double-stage plant for verticalelutriation (e. g. for separating small coal from gangue).

Referring to Figs. 1 to 4, the vertical vessel for separation is made oftwo slightly conically upwardly tapering parts I and 2, which areflanged to one another. Approximately in half of the height of thevessel there is a pipe 3 tangentially running into the vessel, adaptedfor supply of the material to be separated, e. g. a suspension of amixture of sand of different sizes of grains. Supply of water iseffected in the same way by a pipe 4, emptying funnel-shaped into thereduced lower portion 5 of the vessel. The outlet nozzle 6 isexchangeably connected to the end of the funnel, since its section ofpassage has to be adapted to the size of grains of the coarse materialto be cleared off. At the upper end of the vessel there is provided anoverflow tank 1 with lateral outlet.

Below the overflow I as well as above the supply 3 of the mixture andthe supply 4 of water at the bottom, there are provided in the directionof flow concentric annular guide blades 8a, 8b and 8c, slowing down theextreme flowing in the central part of the vessels I, 2, and acceleratecalming down the eddies.

In order to loosen the conglomerations of grains at the bottom of thepipe 3 for supply of the mixture, a separate Water supply 9 is providednear its mouth at the vessel I, 2 thus preventing from droppingconglomerated grains of different sizes complete in themselves. The pipe9 empties from the underside into the supply pipe 3,-and is providedwith a flat enlargement ID in the moving direction of the material,which enlargement fills up the lower portion of the cross-sectional areaof the pipe 3.

Another effective measure for loosening the conglomerations of grains inthe supply pipe 3 consists in leading the mixture to be sorted in thevertical direction which is changed into a horizontal one only at apoint near to the inlet into the separating vessel I, the additionalwater entering the pipe 3 in a tangential direction by the pipe 9 at thebend, (Fig. 2) resulting in thoroughly whirling up the grains. Herebyarising rotation of the liquid in the pipe 3 is capable of being stoppedby a suitably fashioned guide blade 3a or by several ones.

The operation of the apparatus is as follows:

The mixture of sand to be sorted and inflated by water enters theseparating vessel I, 2 by the pipe 3. The conglomerations of grainsforming during the horizontal motion in the pipe 3 are loosened by meansof the auxiliary pipe 9 shortly before entering the vessel. Theapproximately tangential direction of the material entering through thepipe 3 effects rotation of the liquid being present in the space R4. Theliquid in the space R1 is rotated by the pure water entering the lowerportion of the apparatus by the pipe 4 likewise in a tangentialdirection. The supply pipes 3 and 4 are dimensioned in accordance withthe sizes of the vessel and the outlet nozzle 6 in such a way, that thevertical speed of the liquid in the space R4 amounts to about 1dm./sec., in higher levels to slightly increased speeds and in lowerlevels to slightly reduced ones. The finer portions of the sand aretaken along by the rising liquid column in the space R4 and finallywashed away by the overflow I. -The portion of the grains having forinstance a size of more than 0.5 mm. is separated off in the space R5,and continuously moves down into lower levels. The concentric guideblades 8a to guarantee the untroubled flowing in the space R5, uniformover the entire cross-sectional area. The share of larger size of grainscontinuously moves down through the space R: and is freed from theportions of finer grains (less than 0.5 mm. diameter) taken along, bythe liquid rising in the space R2.

The portion of the mixture of grains exceeding 0.5 mm. in size drops inthe space R1 to the nozzle and is taken along by the outlet.

The superiority of the process of vertical elutriation compared withthat of sorting by wet screenant-mm ingbecomem-fullyapparent'fronnthe;following. table of analyses:

Wet; screen; sorting: (quantity worked up 4"Icg.

- square metre and minute) Althoughthe.- prime. cost. of. an apparatusfor vertical elutriation: isone tenth of thatfor wet screen separationthe exactness of. sorting. was possible-tobe improved to; such anextent, that the maximum .sizesof grainskept limited to. about :5 mm:(comparedawithabout. 1, mm. according to the, known. process).whereas-thelosseswere reduced from29.%; to. 1.8

The great importance-ofthis result especially for. manufacture of' glass.becomesevident. from the fact, that: the space oftimerequired formeltinginthe-meltingkettledepends on-the diameter of the; largest.grains-,;almost independently from the-proportion of the sameflout not.on the. aver.- age. diameter. of. the.- sand. for glass -ma-hing;

Another important lineof usingthe. vertical elutriation: is.theproduction; ofkaolin. I In most ofv the. applicationpotkaolin; theexistence of coarse components, which are-caughtr bya screen of. 10,000meshes/square cm. (i. e.,' a diameter of grain. exceeding 0.06 mm.) iundesirable.

It isnot possibleto-exactlyseparate a mixture of kaolinandfine sand asexisting. inthe working up of raw kaolin, by meansof "the usual methodsof. horizontal elutriation (continuous or discontinuous. ellutriation inchannels, .hasins,. etc.) or of. centrifuges providediwith nozzles.Figs. 5. to 8 and Figs.. 9' and 1.0 of" the drawings illustrate. by wayofexample wholesale plants for that purpose. in which figures likefigures of reference indicate the parts corresponding with those ofFigsl to. 4;.

The mixture of- 'kaolin and fine sand to be sorted issuppli-ed' informof a suspension to" the periphery and the middle portion of thelspace Reby: means of pipes. 3... H v

A stirrer; very slowly revolving-having eight blades II is; arrangedimthe. axis. ofisth'e vessel. and effects the uniformdistributionof the.mixture over thewhole. cross-seetionaL-area. of; the liquid.v 1 ;i

Eure. Water. is supplied to the lower portion of. the: vessel by meansof pipes 4' having their mouths. at different. distances. fromtheaxisrespectivelv. the. waterbeingdistributedby eight stirrer bladesll (Figs. 5 to-8).. I

It. is also possible to supply the material to: be

workedmpz-throuemthezaxleor.the-stirrenformed into a hollow. axlea;causing. thesxmcterial. to dis.- chargezfrom; the. stirrer; .blad'esat,points. having different; distancesrfrom; the. axis. respectively. thuspossibly reducing. .turbulences: in the space The vertical: components.of the: speeds: of the liquid in; the spaceRaslightlyexceed those, ofthespace-Ra. Their amounts: dependon the. specific weights oftherawmaterial.tov be-workedumand of. its;admixed;substances;-as:wel1.as: on. the average shape...o.i the.- particles. (In; an,individual case the vertical;- components in the, space: R4 amountedtolimmrlsec.)

The kaolin. (that is: the. particles having. size of grain of less than0.06 mm.) is freed from the coarse grains in the. space R5, and isremoved. by theoverflow-through the tank, 1. A: conical guide blade; [3and apertures; Mot-the. cover 15 prevent noneunifornr .flowingfromadvancing into, the space. R5; which. nonrunitorm; flowing might becaused; by: portions of; tamer-flowing of. the-.overflown The slick.;(pa;rtioles; of 'morethan. 0106.;mm. diameter)" continuously moves.down- .the space Rz;.where; itis freed from the remaining particles of.kaolin... and? finally. continuously escapes through: the .outlet nozzle6 in form. of .a'concentrated suspension.

shownv in Figs. 9.. -.and. 10, the water: suspended mixture of.kaolin-andjsand; to :.be sorted; is supplied. by the pipes 33 to a wideannular jacket l6. surroundingzthe; separating vessel l, 2-, whichjacket-. -heing high. enough as; to. enable; the; drop.- pingparticles.- to. beyuniformly' distributed. over the whole peripheralarea of the inlet slotl'l; prior to; entering: the ,vessel' I- In. the;same way the washing: water: is. supplied: by pipes: 43 to. the annularjacket; I18: with thedischarging slot. 19.

Tests. haveprovedthatwith a single vertical elutriation. (theconstructional height of the separatingyessel. was five. times thediameter of the cross-sect-iorriofthe; liquid) considerably betterresults havevbeen obtained :as by a threefold; horizontal; elntriation,.as thev following fig- 111163551103:

' 3-fold horizontal elutriation single-verticalelutriation kaolin 071%coarse shares, more than.

In the two-stage vertical elutriation, plantas, diagrammatically shownin Fig. 11, separating in the vessel 20 is executed according to a smallcritical speed of fall, whereas the coarse grained discharged. materialis anew sorted in another separating vesselZl according to a greaterspeed 'of' fall; resulting in a'reduction of the constructi'onal heightof the plant.

The water tank." is. provided .witha perina- 7 l nently running overflow23. thuskeeping the 0 water in the tank at the same level. The Waterruns freely by nozzles 24 of a certain size into the intermediatevessel's 25 to 29. thus ensuring the supply: to the same keepingconstant. The .airrhubhle takenalongareenabled to risein thoseintermediate vessels;- 25 to 29.: as. the speed or the According to. thesimplified. embodiment as liquid moving down in the said vessels is aslow one (less than 10 cm./sec.), thus being prevented from producingturbulences in the vessels 20, 2| Changing resistances within the same,it is true, effect changing the levels in the intermediate vessels to29, but they have no influence to the quantities of supply, as the waterfreely crosses the interposed space of air. The mixture of grains to besorted is supplied to an auxiliary vessel provided with a water supply3! and having its upper ortion wide enough as to enable great airbubbles. The conduits 32 and 34 supply water to the bottom of theseparating vessels 20 and 2| respectively, and the conduits 33 and 35the water for diluting the mixture.

In the overflows of the separating vessels 20 and 2| there is only aslight concentration of grains. The concentrated portion is separatedfrom the superfluous water preferably running off the level of thefunnels 36, 31, and is discharged by the nozzles 38, 39. Theconcentration of the discharged material may be auto matically adjustedby a float gauge (not shown in the drawings), the conical lower part ofwhich preferably operating within the outlet nozzle and is raised incase of increasing of the concentration within the funnel, thusenlarging the outlet cross-section of the nozzle.

In case great constructional heights are available, separation may becarried out first by the greatest speed of fall, and the fine grainedshare may be anew subjected to a separating process by a reduced speedof fall, the overflow from the concentrated masses in the funnels may beused as washing liquid in the subsequent separation.

The usual sedimentation process for separating materials of differentdensities such as coal and gangue, fails in case of fine grained coal.

Using vertical elutriation, however, succeeds in separation of evenfiner grained coal particles from gangue, which separation otherwise ispossible to be obtained but by flotation.

For the design of a vertical elutriation it is necessary first of all toascertain the speeds of fall of the concerned coal and the concernedgangue by different sizes of grains in a water column. If the greatestsize ofgrains, for which vertical elutriation is still considered to beeconomical, is assumed to be 8 mm., the screen of the next fineness,determining the lower limit of the first fraction of screened materialfor vertical elutriation, is found out by the condition, that the speedof fall of the grains of coal with a size of 8 mm. has to be smallerthan or at most equal to that of the concerned sizes of grains of thegangue.

The following values have been found in a special case:

After dry screening by a screen of 3 mm., 2 mm., 0.3 mm. size of meshrespectively, the coarsest share (8-43) mm. is vertical elutriated witha speed of 12 cm./sec., the middle one (2-0.3

mm.) with that of 5 cm./sec., and.v finest one (less than 0.3 mm.) with1.2 cm./sec.

In vertical elutriation Of the coarsest share (grains up to 8 mm.)either an outlet nozzle of at least 40 mm. internal diameter isrequired, the water consumption of which appears economic only in caseof great quantities to be worked up, or the coarse grains are removed ina mechanical way, for instance by means of a bucket elevator.

The vertical elutriations of the two first said fractions result in acomplete separation of the coal from the gangue, and in the third onethe discharged coal still contains those usually slight additions ofgangue, the size of grains of which being less than 0.1 mm.

What I claim is:

1. A process for the selective classification of grains by theirdifferent speeds of fall in a column of rising liquid, which processcomprises admitting a separating liquid to the lower part of a separatorvessel to form a column of rising liquid, introducing into a liquidsuspension of the grains to be classified a liquid jet for agitating andloosening up said liquid suspension, directly admitting said liquidsuspension in a loosened-up condition to the column of liquidapproximately at the center of the height thereof immediately after theinjection of the liquid jet into said suspension, controlling theadmission to said liquid column, of said separating liquid, of theliquid for the suspension of grains, and of the liquid for said jet, forconstant relative rates and accelerating gradually and practicallycontinuously the vertical velocity of the liquid in the vessel from thepoint of admission of the separating liquid to the top of the column.

2. A process as claimed in claim 1, which comprises admitting theseparating liquid, the liquid for the suspension of grains, and theliquid for said jet, out of a common liquid supply at a constant rate ina free jet into a deaerating vessel for each of said liquids, andfeeding each of said liquids from its deaerating vessel to its point ofadmission adjacent to the separator vessel.

3. A process for the selective classification of grains by theirdifferent speeds of fall in a column of rising liquid, which comprisesadmitting a separating liquid to the lower part of a separator vessel toform a column of rising liquid, rotating said column of liquid about itsvertical axis, introducing into a liquid suspension of the grains to beclassified a liquid jet for agitating and loosening up said liquidsuspension, admitting directly to said liquid column approximately atthe center of the height thereof tangentially in the sense of rotationof the liquid column said liquid suspension in a loosened-up conditionimmediately after the introduction of said liquid jet into saidsuspension, controlling the admission to said liquid column, of saidseparating liquid, of the liquid for the suspension of grains, and ofthe liquid for said jet, for constant relative rates and acceleratinggradually and practically continuously the vertical velocity of theliquid in the vessel from the point of admission of the separatingliquid to the top of the column.

4. A process as set forth in claim 3, comprising braking the flow ofliquid in a core portion of the column of rising liquid which coreportion is not subjected to liquid friction at the separator walls, inorder to reduce a high velocity of flow of said core portion relative toother portions of the column and to produce a current composed of twosuperimposed parts, each part having an upwardly widening bottom portionand an upper portion having a continuous upward taper from its lowerend, where its adjoins said bottom portion, at least one liquid supplyconduit tangentially connected to the lower part of the separator vesselat the level of the largest cross section thereof, at least one supplyconduit for a liquid suspension of grains one end of which openstangentially into the upper part of the separator vessel at the largestcross section thereof, and a conduit for additional liquid for agitatingsaid suspension of grains, said conduit for additional liquid beingconnected to said supply conduit for a liquid suspension of grainsadjacent to the end of the latter conduit opening into the separatorvessel. c

6. Apparatus as set forth in claim 5, comprising means consisting ofconcentric sheet metal rings coaxial with the separatorvessel andarranged in a space adapted to accommodate a core portion of the liquidcolumn spaced from the walls of the separator vessel, the height of saidrings exceeding the free radial distance between adjacent rings, atleast one of said guide means being provided between the level where theliquid supply conduit is connected to the separator and the level wherethe conduit for the liquid suspension of grains is connected to theseparator vessel, and at least one of said guide means being providedabove the level where the conduit for the liquid suspension of grains isconnected to the separator vessel.

'7. Apparatus as set forth in claim 5, in which said supply conduit forthe suspension of grains comprises at least one pipe elbow openinghorizontally into the separator vessel and said conduit for additionalliquid comprises at least one pipe opening tangentially at the bottom ofsaid 10 elbow and normal to the direction of flow of the suspension ofgrains in said elbow.

8. Apparatus as set forth in claim 5, which comprises an elevated tank,an overflow adapted to flow continuously, to maintain a constant levelof liquid in said tank, outlet nozzles in said tank, said outlet nozzlesin number and liquid supply rate corresponding to the conduitsfor theseparating liquid, the liquid'of the suspension of grains, andv theadditional liquid, a deaerating tank arranged below each outlet nozzle,said outlet nozzle being adapted to introduce a free jet of liquid intosaid deaerating tank, and each of said conduits leading from therespective deaerating tank to the respective point of admission adjacentto the separator vessel.

' 'I'HEODOR EDER.

file of this patent:

UNITED STATES PATENTS Number Name Date 528,803 Ramsay Nov. 6, 1894636,675 Latimer Nov. 7, 1899 948,513 Lenders Feb. 8, 1910 1,035,864Dallemagne Aug. 20, 1912' 1,143,587 Marsden June 5, 1915 1,205,673Shahan Nov. 21, 1916 1,210,916 Draper Jan. 2, 1917 1,351,234 Draper Aug.31, 1920 1,449,603 Hokanson Mar. 27, 1923 1,516,204 Olsen Nov. 18, 19241,705,351 Andrews Mar. 12, 1929 1,841,444 Hosking Jan. 19, 19321,922,489 Mercier Aug. 15, 1933 1,989,937 Lessing Feb. 5, 1935 2,091,514Meston Aug. 31, 1937 2,346,005 Bryson Apr. 4, 1944 FOREIGN PATENTSNumber Country Date 171,267 Great Britain Nov. 17, 1921

